The present invention relates to N-tert-butoxycarbonyl-2-pyrrolidinones, and a production method thereof.
Conventionally, for N-tert-butoxycarbonylation (hereinafter, abbreviated simply as N-Boc formation in some cases) using di-tert-butyl dicarbonate of 2-pyrrolidinones, there are known a method of using acetonitrile as a reaction solvent (see, Tetrahedron, 61(13), 3271 (2005)), a method of using N,N-dimethylformamide as a reaction solvent (see, WO-2002081442), a method of using tetrahydrofuran as a reaction solvent (see, U.S. Pat. No. 5,024,994), a method of using triethylamine as a reaction solvent (see, WO-9805327), a method of using a non-polar halogen-based solvent (see, J. Org. Chem., 68(19), 7219 (2003)) and the like.
These methods using polar solvents have a problem that if water-washing is performed for the purpose of removing a base used together in the reaction, separation of a polar solvent and water is difficult, thus, washing with water should be carried out after once substitution with a hydrophobic organic solvent. In the case of use of a halogen solvent such as methylene chloride and the like (see, J. Org. Chem., 68(19), 7219 (2003)), there is a problem of toxicity of the vapor of the solvent. That is, all the methods are not necessarily satisfactory as an industrial production method.
The present inventors have investigated a method for N-Boc formation of 2-pyrrolidinones, showing little of the problems as described above, and resultantly found a method of N-Boc formation of 2-pyrrolidinones in an aromatic solvent. Further, the present inventors have found novel N-tert-butoxycarbonyl-2-pyrrolidinones.